1) Field of the Invention
The present invention relates generally to a truss beam, and particularly to a truss beam comprised of rods, shear web panels, and self-aligning adapters.
Unidirectional fiber composite rods present an attractive option for structural members for use in applications requiring high strength and minimum weight, including but not limited to: spacecraft, aircraft (especially rigid airships), high performance ground vehicles, sports equipment (e.g. hang gliders), and tall architectural structures. To fully exploit the bending and compressive strengths of such assemblies composed of unidirectional fiber composite rods, one must provide for buckling stability.
The enormous strength of unidirectional fiber composite rods is difficult to fully exploit because of the difficulty in joining the rod ends to metal components. Bolting does not work with unidirectional composites, and bonding is difficult due to stiffness mismatches between the composite and metal components and the general lack of surface area per volume. Ideally, a thick bond is desired so that the relatively softer adhesive can shear and distribute shear stresses more uniformly instead of peaking at the ends of the bond. Thick bonds are difficult to obtain and repeatably control with conventional methods of beads, bonding wire, shim, or tooling. Most of these methods control the minimum thickness of the bond, but do not control the maximum thickness. In addition, traditional joint types such as lap, strap, scarf, etc. are not ideal for this purpose due to the non-planar nature of rods, fabrication costs, and strength issues.
2) Description of the Prior Art
U.S. Pat. No. 4,729,605 by Imao et al discloses a bicycle wheel spoke comprising a fiber reinforced plastic rod having metal parts adhesively bonded to the ends of the plastic rod, the plastic rod ends having been inserted into bores in the metal parts. U.S. Pat. No. 5,350,221 by Pearce et al discloses a wheel spoke comprising a fiber reinforced plastic shaft having metal end pieces adhesively bonded to the ends of the plastic shaft. U.S. Pat. No. 6,374,445 by Fuessinger et al discloses a tension rod for a chord for a bridge comprising a middle part made of a fiber composite material, the ends of which are glued to metallic end parts. U.S. Pat. No. 5,655,347 by Mahieu discloses a biarch framing member wherein at least one of the arches is made from a fiber reinforced polymer. U.S. Pat. No. 6,446,292 by Fuessinger et al discloses a mobile bridge utilizing composite fiber belts (for tensile forces) to which are attached shear ribs (for shear forces). U.S. Pat. No. 4,932,807 to Rhodes discloses an example of a clevis joint for use in a truss structure.